The invention relates to a link element of variable effective supporting length for the spring drive of a pivoting component, especially for the pivoting drive of a structural member of a vehicle folding top. The link element is articulated at a distance from the pivot axis of the pivoting component between the latter and a counter-component. The effective supporting length of the link element is variable during the pivoting of the pivoting component as a result of the deformation of an accumulator spring.
A link element of this type is to be taken as already known, for example, from German Patent Application G 89,211, wherein the link element is of variable length as a result of a telescopic design. Supported axially between the interacting telescopic tubes of the link element is a helical compression spring which is surrounded by the tubes and which serves as an accumulator spring for the spring-driven closing of the folding top. For this, one telescopic tube of the link element is articulated on a front roof-frame part and the other telescopic tube on a rear roof-frame part of a lateral roof frame which is designed as a two-part folding frame.
During the closing of the folding top, the link element lengthens as a result of the expansion movement of the accumulator spring, with the result that the front roof-frame part and consequently the entire front roof part is pivoted relative to the rear roof-frame part into an extended position occupied with the folding top closed.
Instead of the helical compression spring as an accumulator spring, alternatively, there is a tension spring, by means of which the folding top can be thrown open in a spring-driven manner, with the arrangement of the link element being unchanged. The front roof part would thus be pivoted upwards relative to the rear roof part in a first opening phase of the folding top.
The known link element involves a relatively high outlay in manufacturing terms and is therefore expensive to produce. Moreover, its telescopic design necessitates a considerable space for the arrangement and movement of the link element, and this will not be immediately available where many folding-top versions or other instances of use are concerned. This is all the more so because, by being articulated at both ends, the link element, although having the appearance of a link, nevertheless can no longer fulfill the function of a genuine link.
Furthermore, pivoting components which have to be spring-driven only through a relatively small pivoting angle are known.
As regards folding tops, attention is drawn in this respect to German Patent Specification 651,973 which discloses a folding top. The front roof part of the top is pivoted upwards in the first phase of the opening movement into a lifted-off intermediate position by means of a spring-accumulator drive, after which the folding top can be thrown open more easily. Here, the accumulator springs are two sleeve springs which are each integrated in a bush-like manner into an associated hinge joint between the front and rear roof-frame part of a lateral roof frame. These sleeve springs consist of an elastomeric material and act as turn and slide springs between a cylindrical inner and outer sleeve of the hinge joint. Radial stop means serve for limiting the driving pivot angle.
The sleeve springs provided as accumulator springs make it possible in a way advantageous per se to do without the use of link elements of variable length for the pivoting drive. On the other hand, the integration of the sleeve springs into the associated hinge joint presupposes a large-size joint design. Where folding tops having relatively slender roof frames or other pivoting components are concerned, the necessary installation space will not be directly available in terms of construction for a joint design of this type. Therefore, sleeve springs of the known type which are used as accumulator springs cannot be employed.
There is therefore needed the development of a link element of variable effective supporting level for the spring drive of a pivoting component of the relevant generic type, to the effect that although the pivoting component can be spring-driven by means of the link element, only over a relatively small deflection angle the kinematically movement-controlling link characteristic of a link component will be largely preserved.
The present invention meets these needs by a link element of variable effective supporting length for the spring drive of a pivoting component. The link element is articulated at a distance from the pivot axis of the pivoting component between the latter and a counter-component. The effective supporting length of the link element is variable during the pivoting of the pivoting component as a result of the deformation of an accumulator spring. With the link element being of constant length per se, the accumulator spring is formed by an elastic element located at the articulation on the pivoting component and/or counter-component. To regenerate the accumulator spring, the rigid link is displaced longitudinally relative to a bearing lug of the connecting component, the accumulator spring being correspondingly compressed.
To allow the articulation by means of accumulator springs of short spring excursion, the two ends of the link can be articulated by means of an accumulator spring, the spring excursions of which supplement one another.
Since the accumulator spring or the accumulator springs allow only a narrowly limited relative displacement of the link in relation to the bearing lug or the axial pin of the connecting component, the link element can advantageously replace a controlling link, necessary in any event, of an articulated parallelogram or the like.
If a parallelogram linkage comprises a plurality of parallelogram-like four-bar mechanisms which are arranged in succession in the manner of a scissor mechanism, each of the four-bar mechanisms can have a control link designed as a link element of variable length. Since the spring excursions of the accumulator springs used on all the control links are added together, a relatively long total spring excursion is brought about even with the use of accumulator springs which each have a short spring excursion.
The accumulator spring preferably consists of a radially elastic sleeve spring, for example made of rubber, which is arranged in a similar way to that of a bearing bush. Such sleeve springs can be produced cost-effectively. Furthermore, compression of such sleeve springs in any radial direction is possible.
To drive the pivoting component out of one of its end positions, the constructive supporting length of the link element appropriately differs from the non-loaded supporting length of the link element to such an extent that the accumulator spring or the accumulator springs are exactly regenerated in the end position of the pivoting component. Undesirable overstretching of the accumulator springs can thereby be reliably prevented.
By means of a mirror-symmetric arrangement of a plurality of link elements in the parallelogram linkage of a folding-top structure, a front roof part of a folding top can be driven in a simple way into an upwardly pivoted intermediate position and held automatically in this position.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.